The invention relates to a laser illumination arrangement for illuminating a photosensitive layer in the course of the manufacture of a cathode ray tube, said laser illumination arrangement comprising a laser and an optical imaging arrangement for imaging laser light onto the photosensitive layer which is applied to a display window of or for a cathode ray tube.
Such illumination arrangements can be used to manufacture a cathode ray tube, inter alia, for creating phosphor patterns and black matrix patterns on a display window of a cathode ray tube.
An illumination arrangement of the type mentioned in the opening paragraph is disclosed in U.S. Pat. No. 4,117,177. In this patent specification, a description is given of an arrangement in which a photosensitive layer is illuminated by means of a laser beam. The photosensitive layer is applied to a surface of a display window of or for a cathode ray tube. Illumination takes place by imaging laser light onto and scanning it across the photosensitive layer. A shadow mask comprising a large number of openings is situated between the illumination arrangement and the photosensitive layer. The laser light is directed through the openings in the shadow mask at such an angle that a pattern is formed behind the shadow mask. This process is repeated a number of times, at a number of different angles, thereby creating a number of patterns. In this manner, phosphor patterns and/or black matrix patterns can be provided.
Although the use of a laser for illuminating the photosensitive layer offers a number of advantages, it has been found in practice that by using the above-described method, the illumination pattern is subject to variations, leading to an increase of the number of rejects (=the number/percentage of illuminated photosensitive layers which do not meet the quality requirements imposed and hence must be removed from the production process).